Green hydrogen: solar-powered photochemical water splitting on InGaN nanowire arrays

全球能源正处于巨大变革的风口浪尖，许多人预测，新兴的氢经济可能最终取代推动工业革命的碳经济。在这方面，已经深入研究了光化学水裂解，其使得能够将太阳能直接转化为氢基燃料。在过去的四十年里，纳米材料的发展主要集中在以粉末形式使用的大带隙金属氧化物上。然而，这种基于氧化物的方法遭受两个基本的效率瓶颈：弱的光子吸收和差的激子分离，这分别是由于氧化物固有的大带隙和粉末结构的有限表面积。在这个项目中，作者建议研究InGaN纳米线阵列上的光化学水分解，这可以导致高效的太阳能到氢气的转换。与金属氧化物相比，通过改变合金成分，InGaN的能带隙几乎可以涵盖整个太阳光谱。此外，纳米线表现出极大的表面积与体积比，显着增强的光吸收，和更有效的电荷分离，有望大大增强光催化活性。作者最近在世界上首次实现了使用金属氮化物纳米线的光催化整体水分解和氢气生成。在该项目中，作者将进一步开发基于上级质量、多结InGaN纳米线的光催化剂，该光催化剂可以吸收大部分太阳光谱，并可以在太阳照射下驱动高效（>15%）制氢。通过解决实现稳定，高效的水分解和直接从太阳辐射制氢的巨大挑战，该项目将为快速发展的太阳能和氢产业提供范式转变。

The global energy is on the cusp of immense change, and it has been projected by many that the emerging Hydrogen Economy may eventually replace the Carbon Economy that fuelled the industry revolution. In this regard, photochemical water splitting has been intensively investigated, which enables the direct conversion of solar energy into hydrogen based fuel. Over the past four decades, the development of photocatalysis has primarily focused upon large bandgap metal oxides employed in the form of powders. However, this oxide based approach suffers from two fundamental efficiency bottlenecks: weak photon absorption and poor exciton separation, due to the inherently large band gap of oxides and the limited surface area of powdered structures, respectively. In this project, the authors propose to investigate the photochemical water splitting on InGaN nanowire arrays, that can lead to high efficiency solar-to-hydrogen conversion. Compared to metal oxides, the energy bandgap of InGaN can encompass nearly the entire solar spectrum by varying the alloy compositions. Moreover, nanowires exhibit extremely large surface-to-volume ratios, significantly enhanced light absorption, and more efficient charge separation, promising drastically enhanced photocatalytic activity. The authors have recently achieved, for the first time in the world, photocatalytic overall water splitting and hydrogen generation using metal-nitride nanowires. In this project, the authors will further develop superior quality, multi-junction InGaN nanowire based photocatalysts that can absorb a large part of the solar spectrum and can drive high-efficiency(>15%) hydrogen generation under solar irradiation. By addressing the grand challenges for achieving stable, efficient water splitting and hydrogen generation directly from solar irradiation, this project will provide a paradigm shift in the rapidly evolving solar energy and hydrogen industries.